Some Antinutritional Factors in Moringa peregrina (Al-Yassar or Al-Ban) and Soybean Products HASSAN A. AL-KAHTANI ABSTRACT Mon’ngu peregrina and soybeandefatted flours, protein concentrates, and isolates were assayed for trypsin (TIA) and cx-amylase (AIA) inhibitor activities, phytic acid, tannin and chlorogenic acid contents, and in vitro protein digestibility QVPD). TIA in M. pevegrina defatted flour (MDF) was lower (P < 0.05) but more heat resistant than in soybean. AL4 in MDF was lower than in soybean and inhibited pancreatic amylase more than bacterial amylase. Some M.peregrina products were higher in phytic acid but lower in chlorogenic acid than soybean. Tannin was low in all samples.IVPD was slightly lower for M.peregrinu than for soybean. Key Words: soybean, antinutrients, flour, protein concentrate, trypsin INTRODUCTION MORINGA PEREGRINA [Syns=Moptera Gaerton., M.arabica (Lam) Pers.] is one of about 10 xerophytic species of the family Moringaceae (FAO, 1988). Details on such plants, including English and French names, botanic characteristics, world distri- bution, chemical composition, and uses have been published (Migahid, 1978; Somali et al., 1984; FAO, 1988; Al-Yahya et al., 1990). The chemistry of crude oil (>54%) (Al-Kahtani, 1993), and the physical, chemical, and functional properties of M.peregrina proteins (Al-Kahtani and Abou-Arab, 1993) were also reported. The meal remaining after extraction of oil con- tains about 57% protein and could be a very important protein source if it is suitable for human consumption. Nutritive quality or digestibility of a protein is affected by the presence of antinutritional factors, such as enzyme inhibi- tors, phenolic compounds, and phytate (Carter et al., 1972; Hsu et al., 1977; Powers and Whitaker, 1977; Granum, 1979; Erd- man et al., 1980; Tan et al., 1983; Cinco et al., 1985; Kumar and Chauhan, 1993; Mameesh and Tomar, 1993; Ologhobo and Fetuga, 1984). No determination of antinutritional factors in M.peregrina has been made. This work is a continuation of our earlier study on M.peregrina products (Al-Kahtani and Abou-Arab, 1993). The objective was to evaluate several possible antinutritional factors in M.peregrina and compare them with soybean products, and to assess the in vitro protein digestibility of those products. MATERIALS & METHODS Materials Seeds (kernels) of M.peregrinu were obtained from Al-Ola region, Northwest Saudi Arabia. Soybeans(cv. Jupiter) were obtained from Ag- ricultural Experiment Station, College of Agriculture, King Saud Uni- versity, Riyadh, Saudi Arabia. Seeds were cleaned, hand-cracked, dehulled and pulverized with a Waring commercial blender (Sanyo Elec- tric Co. Ltd., Japan) at speed 1 for 15 sec. Soybean seedswere milled to pass through 0.5 mm sieve using an Ultra-Centrifugal mill (Resh type ZMI, F., Kurt Retsch Gmb H & Co., Germany). Author ACKahtani is affiliated with the Food Science Department, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia. Preparation of defatted flour, protein concentrate, and protein isolate Full fat flours from M.peregrina and soybeans were prepared as de- scribed (Al-Kahtani and Abu-Arab, 1993). The defatted meals were air- dried for 24 br at room temperature (-25°C) and then ground into flour (180ym particles). Protein concentrate was prepared from the defatted flour according to the methods of Mattil (1974). The method of Sosulski et al. (1978) was used for preparation of protein isolates. Protein con- centrate and protein isolates were dried and ground into flour (180~pm particles). Trypsin inhibitor activity assay Trypsin inhibitor extracts were prepared as describedby Roy and Bhat (1974). Four g powdered samples were extracted with 40 mL 0.05M sodium phosphate buffer, pH 7.0, and 40 mL distilled water. Samples were shaken for 3 hr and then centrifuged at 10000 rpm for 30 min, and supematants were filtered. All extracts were diluted 10 times with ap- propriate diluents for analysis of trypsin inhibitor activity (TIA). The method of Roy and Rao (1971) was employed for determining TIA in each extract using Bovine pancreas, type III (Sigma Chemical Co., St. Louis, MO). Trypsin inhibitor activity was calculated as the number of trypsin units inhibited per mg dry sample. Thermal stability of trypsin inhibitor activity Trypsin inhibitor extracts were heated at 95°C for specified times up to 5 hr. Aliquots were removed, cooled rapidly in an ice bath, then subjected to inhibitory activity assay according to the procedure of Roy and Rao (1971). wamylase inhibitor activity assay Amylase inhibitors were extracted according to the method of Cinco et al. (1985). Five g powdered samples were extracted by stirring for 2 hr in 125 mL 0.02Msodium phosphatebuffer (pH 6.9) containing 0.15 M Nacl. The extract was cenhifueed at 10000 mm for 15 min. Insoluble matter was discarded and inhibit& activity was measured in the super- natant as described by Deshpande et al. (1982). Porcine pancreatic o- amylase (type 1 -A, 2 X crystallized Sigma Chemical Co., St. Louis, MO) and bacterial source a-amylase, (BDH) were the sources of enzyme in- cubated with inhibitor extracts. One unit of enzyme activity was defined as that which liberated from soluble starch 1 mg maltose/min at 37°C and pH 7.0 under the specified conditons. Thermal stability of a-amylase inhibitor activity a-amylase inhibitor extracts were heated at 70°C in a water bath for specified times up to 120 min. Aliquots were removed, cooled rapidly in an ice bath, then subjected to inhibitory activity assay according to the procedure of Deshpandeet al. (1982). Phytic acid Phytic acid content was determined using chromophore reagent as described by Mohamed et al. (1986). Tannin content The method of Bums (1971) as modified by Maxson and Rooney (1972) was used: l-g sample was extracted with 10 mL 1% HCl in methanol for 24 hr atroom temperature (=25”C), with mechanical shak- ing. After centrimgation at 10000 rpm for 5 min, 1 mL supematant was Volume 60, No. 2, 1995-JOURNAL OF FOOD SCIENCE-395 I